Supersonic whistle for code communication



Oct. 16, 1951 R. c. WILLMAN 2,571,640

SUPERSONIC WHISTLE FOR CODE COMMUNICATIONS Filed May 12, 1 945 INVENTOR.Flew/120 C Mum/w A TTORNEY Patented Oct. 16, 1951 SUPERSONIC WHISTLE FORCODE COMMUNICATION Richard C. Willman, Indianapolis, Ind., assignor toRadio Corporation of America, a corporation of Delaware Application May12, 1945, Serial No. 593,500

7 Claims.

tain a more uniform air pressure applied to the whistle, thereforekeeping the output frequency more nearly constant.

A feature of this invention is the arrangement of a whistle with animproved mouthpiece having a relief valve attached thereto.

Supersonic code communication equipment generally includes a smallwhistle which is blown by the mouth and tuned to any frequency between15 and 26 kilocycles per second. A sharply tuned receiver which is tunedto the same frequency as the whistle is used to receive the codecommunication. The receiver usually employs an oscillator which isarranged to beat With the supersonic frequency to produce an audiblesignal. It has been found that the output signal frequency from thewhistle varied so greatly with the air pressure that it was difficult toblow the whistle so thatits output would be received properly by thesharpl tuned receiver. This invention overcomes the difliculty bymaintaining more uniform air pressure by providing an improvedmouthpiece having a relief valve associated therewith.

This invention will best be understood by referring to the accompanyingdrawing in which:

Fig. 1 is a longitudinal section of the whistle of this invention, and

Fig. 2 is a cross section of Fig. 1, the section being taken on line 22.

Referring now in detail to the drawing, the body portion of the whistleincludes a long cylindrical member I, which may be constructed of metal.At a suitable portion along the length of member I, there is provided anaperture 2 which is tapered at 3 to provide a sharp edge at portion 4.The length of the resonant air chamber between the end plug 5 and. a rodmember 6 is determined by the frequency at which the whistle is tooperate. The rod shaped portion 6 is secured to the inner wall of memberI, the upper portion being cut away to provide an air passage or chamberI. A mouthpiece 8 is shaped at S to receive the outer portion of body Iand the forward end is suitably shaped at In to form the usualmouthpiece. Intermediate the portions 9 and I0, there is located aslotted portion I I and a flattened portion I2. Surrounding the portionsII and I2, a thin Phosphor bronze spring I3 is suitably shaped to belocated with the portions II and I2 and held by its own tension over arelief valve hole I4. The tension of spring I3 is adjusted to open atany predetermined desired pressure. Inthe operation of this device whenit is desired to transmit code signals the mouth piece In of the whistleis placed in the mouth and the operator blows a jet of air through theair passage I which impinges the knife edge 4 causing a supersonicfrequency wave to be emitted from the resonant air chamber. If theoperator should blow the whistle too hard or with an uneven pressure thespring tension relief valve l3 will open until the pressure is reduced.

In a device which was constructed, a half pound per square inch pressurewas chosen. As long as the whistle is blown hard enough to open thespring, the pressure on the whistle will not be appreciably aboveone-half pound per square inch.

The size of aperture I4 is sufliciently large to accomplish this whenthe unit is blown by any air pressure capable of being created by lungpower. The vibration of the spring I 3 when opened tends to impart awarble to the emitted signal which is desirable for this type of codeapplication. The sound of the escaping air can be silenced by theaddition of layers of absorbing material over a plurality of escapeholes of apertures I5, l6 and H which are provided on the metallic coverring member I8.

What is claimed is:

1. A structure for producing substantially constant frequencycompressional waves in response to continuous application of a fluidvarying in pressure over a wide range of pressures, including a hollowbOdy portion having fluid inlet and outlet apertures and an orificelocated between said apertures, and a resilient member subjected to theflow of said fluid and positioned with respect to said orifice to form aclosurefor the same, said resilient member effectively adjusting saidorifice to bypass a portion of said fluid to maintain substantiallyconstant pressure at said outlet aperture.

2. A structure for producing substantially constant frequencycompressional waves in response to continuous application of a fluidvarying in pressure over a wide range of pressures, including a hollowbody having a resonant chamber, said chamber having fluid inlet andoutlet apertures and an orifice located between said apertures, and aresilient member subjected to the flow of said fluid and positioned withrespect to said orifice to form an adjustable closure for the same, saidresilient member being effective to open and close said orifice tobypass a portion of said fluid to maintain substantially constantpressure at said outlet aperture.

3. A structure for producing substantially constant frequencycompressional waves in response to continuous application of a fluidvarying in pressure over a wide range of pressures, including a bodyportion having a resonant chamber having fluid inlet and outletapertures leading into and out of said chamber, a mouthpiece having abore adapted to communicate with said fluid inlet, and an orificeleading from said bore to the exterior of said mouthpiece, and aresilient member arranged internally of said mouthpiece and subjected tothe flow of said fluid, said resilient member being positioned withrespect to said orifice to form an adjustable closure for the same, saidresilient member being adjusted effectively to bypass all of said fluidabove a predetermined amount to maintain substantially 4 constantpressure at said outlet aperture.

4. A generator for producing substantially constant frequencycompressional waves in response to continuous application of a fluidvarying in pressure over a wide range of pressures, including a bodyportion comprising a hollow tube having one end closed and an outletaperture, said tube having the dimensions between said closed end andsaid outlet aperture to provide resonance at the desired frequency, amouthpiece connected to the open end of said tube, said mouthpiecehaving an annular bore therewithin and a relief valve hole leading fromsaid bore to the exterior, and a spring tensioned valve memberpositioned in said bore to cover said relief valv hole, said springtensioned valve member being adjusted to bypass all of said fluid abovea predetermined value to maintain substantially constant pressure atsaid outlet aperture.

5. A structure providing a uniform air pressure front in response tosteadily applied air of varying pressure, including a hollow memberhaving an elongated bore therethrough, an annular bore surrounding saidelongated bore, said member having a relief valve hole interconnectingsaid bores, and a relief valve spring arranged in said annular bore tocover said relief valve hole, said spring being adjusted to bypass airapplied at one end of said elongated bore above a predetermined value toproduce substantially constant pressure at the other end of saidelongated bore.

6. A structure providing a uniform air pressure front in response tosteadily applied air of varying pressure, including a hollow memberhaving an elongated bore therethrough, an annular bore surrounding saidelongated bore, there being a fiat surface in said annular bore, saidmember having a relief valve hole arranged in said flat surface tointerconnect said bores, and a relief valve spring arranged in saidannular bore, said relief valve spring having a flat portion arrangedvto cover said relief valve hole, the flattened portion of said springbeing arranged to bypass air applied at one end of said elongated boreabove a predetermined value to produce substantially constant pressureat the other end of said elongated bore.

'7. A structure providing a uniform air pressure front in response tosteadily applied air of varying pressure, including a hollow memberhaving an elongated bore therethrough, an annular bore surrounding saidelongated bore there being a flat surface in said annular bore, saidmember having a relief valve hole arranged in said flat surface tointerconnect said bores, and a relief valve spring arranged in. saidannular bore. said relief valve spring having a flat portion arranged tocover said relief valve hole, the flattened portion of said spring beingarranged to bypass air applied at one end of said elongated bore above apredetermined; value to produce substantially constant pressure at theother end of said elongated bore, and a cover band surrounding saidmember' to hold said spring in place, said band having escape holestherein to permit escape of the bypassed air.

RICHARD C. WILLMAN.

REFERENCES CITED The following references are of record in the file ofthis patent:

UNITED STATES PATENTS Number Name Date 39,873 Banks Sept. 15, 1863405,868 Bernardin June 25, 1889 992,487 Ellison May 16, 1911 1,038,074Berrenberg Sept. 10, 1912 1,225,940 Dixon May 15, 1917 1,315,019 HeyerSept. 2, 1919 1,779,795 Backstatter Oct. 28, 1930 2,245,484 Leavens.June 10, 1941 2,376,971 Kleit May 29, 1945

